rust-lang / rust-lang/rust

ICE: `fn_abi_of_instance(foo, [])` failed: Layout(Unknown(Foo))

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A-layout A-repr C-bug I-ICE S-bug-has-test T-compiler
Dominant language
Rust
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Description

auto-reduced (treereduce-rust):

//@compile-flags: --crate-type lib
#![feature(repr_simd)]

const C: usize = 16;

#[repr(simd)]

pub struct Foo([u8; C]);

pub unsafe fn foo(a: Foo) {}

fn main() {}

original:

//! This is a regression test to ensure that we evaluate
//! SIMD vector length constants instead of assuming they are literals.

//@ only-x86_64
//@ check-pass

#![feature(repr_simd)]

const C: usize = 16;

#[repr(simd)]
#[derive(Copy, Clone)]
pub struct Foo([u8; C]);

pub unsafe fn foo(a: Foo) {
        std::str::from_utf8_unchecked(&[99, 108, 105, 112, 112, 121]);
        str::from_utf8_unchecked(&[99, 108, 105, 112, 112, 121]);
        std::str::from_utf8_unchecked(&[b'c', b'l', b'i', b'p', b'p', b'y']);
        str::from_utf8_unchecked(&[b'c', b'l', b'i', b'p', b'p', b'y']);
        std::str::from_utf8_unchecked(b"clippy");
        str::from_utf8_unchecked(b"clippy");

        let x = 0xA0;
        std::str::from_utf8_unchecked(&[0xC0, x]);
        str::from_utf8_unchecked(&[0xC0, x]);
    }

fn main() {}

Version information

rustc 1.87.0-nightly (fd17deacc 2025-03-04)
binary: rustc
commit-hash: fd17deacce374a4185c882795be162e17b557050
commit-date: 2025-03-04
host: x86_64-unknown-linux-gnu
release: 1.87.0-nightly
LLVM version: 20.1.0

Possibly related line of code:
https://github.com/rust-lang/rust/blob/fd17deacce374a4185c882795be162e17b557050/compiler/rustc_codegen_llvm/src/context.rs#L1279-L1291

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zincremental-verify-ich=yes -Cincremental=<dir> -Cdebuginfo=2 -Clink-dead-code=true -Zvalidate-mir --edition=2024

Program output 

warning: unused variable: `a`
 --> /tmp/icemaker_global_tempdir.ROUzTbiGr8Hi/rustc_testrunner_tmpdir_reporting.XbcWx4r0xnnE/mvce.rs:9:19
  |
9 | pub unsafe fn foo(a: Foo) {}
  |                   ^ help: if this is intentional, prefix it with an underscore: `_a`
  |
  = note: `#[warn(unused_variables)]` on by default

error: internal compiler error: compiler/rustc_codegen_llvm/src/context.rs:1285:21: `fn_abi_of_instance(foo, [])` failed: Layout(Unknown(Foo))
 --> /tmp/icemaker_global_tempdir.ROUzTbiGr8Hi/rustc_testrunner_tmpdir_reporting.XbcWx4r0xnnE/mvce.rs:9:1
  |
9 | pub unsafe fn foo(a: Foo) {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^^


thread 'rustc' panicked at compiler/rustc_codegen_llvm/src/context.rs:1285:21:
Box<dyn Any>
stack backtrace:
   0:     0x7421787dad94 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h38d103f25b5fc9da
   1:     0x7421790057e2 - core::fmt::write::h51e5c982d87d838d
   2:     0x74217a2d4511 - std::io::Write::write_fmt::h24e7c9ef42bcecab
   3:     0x7421787dabf2 - std::sys::backtrace::BacktraceLock::print::h2f36236a0c89f5ad
   4:     0x7421787dd4d2 - std::panicking::default_hook::{{closure}}::hfa3a01d30bf38a16
   5:     0x7421787dd0c4 - std::panicking::default_hook::h73a43ec84dfb2d2e
   6:     0x74217792bdd7 - std[5b59e6f68f39e4a3]::panicking::update_hook::<alloc[a5cfa563521ef073]::boxed::Box<rustc_driver_impl[3a7877a37badcc56]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7421787ddd43 - std::panicking::rust_panic_with_hook::h7086c047409dd55a
   8:     0x7421779683b1 - std[5b59e6f68f39e4a3]::panicking::begin_panic::<rustc_errors[e91cd7d082a11be2]::ExplicitBug>::{closure#0}
   9:     0x74217795c7c6 - std[5b59e6f68f39e4a3]::sys::backtrace::__rust_end_short_backtrace::<std[5b59e6f68f39e4a3]::panicking::begin_panic<rustc_errors[e91cd7d082a11be2]::ExplicitBug>::{closure#0}, !>
  10:     0x74217795c5a7 - std[5b59e6f68f39e4a3]::panicking::begin_panic::<rustc_errors[e91cd7d082a11be2]::ExplicitBug>
  11:     0x742177971ec1 - <rustc_errors[e91cd7d082a11be2]::diagnostic::BugAbort as rustc_errors[e91cd7d082a11be2]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x742177ec513c - <rustc_errors[e91cd7d082a11be2]::DiagCtxtHandle>::span_bug::<rustc_span[c14b644df6d3ab3c]::span_encoding::Span, alloc[a5cfa563521ef073]::string::String>
  13:     0x742177f4d66a - rustc_middle[20fb34f80dd5af75]::util::bug::opt_span_bug_fmt::<rustc_span[c14b644df6d3ab3c]::span_encoding::Span>::{closure#0}
  14:     0x742177f34f7a - rustc_middle[20fb34f80dd5af75]::ty::context::tls::with_opt::<rustc_middle[20fb34f80dd5af75]::util::bug::opt_span_bug_fmt<rustc_span[c14b644df6d3ab3c]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  15:     0x742177f34deb - rustc_middle[20fb34f80dd5af75]::ty::context::tls::with_context_opt::<rustc_middle[20fb34f80dd5af75]::ty::context::tls::with_opt<rustc_middle[20fb34f80dd5af75]::util::bug::opt_span_bug_fmt<rustc_span[c14b644df6d3ab3c]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  16:     0x74217685e107 - rustc_middle[20fb34f80dd5af75]::util::bug::span_bug_fmt::<rustc_span[c14b644df6d3ab3c]::span_encoding::Span>
  17:     0x7421777b168d - <rustc_codegen_llvm[c860875266de27e1]::context::CodegenCx as rustc_middle[20fb34f80dd5af75]::ty::layout::FnAbiOfHelpers>::handle_fn_abi_err
  18:     0x7421777899ea - <rustc_codegen_llvm[c860875266de27e1]::context::CodegenCx as rustc_middle[20fb34f80dd5af75]::ty::layout::FnAbiOf>::fn_abi_of_instance::{closure#0}
  19:     0x742179a9ee24 - <rustc_codegen_llvm[c860875266de27e1]::context::CodegenCx as rustc_codegen_ssa[3de69e11977865d2]::traits::declare::PreDefineCodegenMethods>::predefine_fn
  20:     0x742179aa1323 - rustc_codegen_llvm[c860875266de27e1]::base::compile_codegen_unit::module_codegen
  21:     0x74217a0877d0 - <rustc_codegen_llvm[c860875266de27e1]::LlvmCodegenBackend as rustc_codegen_ssa[3de69e11977865d2]::traits::backend::ExtraBackendMethods>::compile_codegen_unit
  22:     0x74217a088d57 - <rustc_codegen_llvm[c860875266de27e1]::LlvmCodegenBackend as rustc_codegen_ssa[3de69e11977865d2]::traits::backend::CodegenBackend>::codegen_crate
  23:     0x74217a07ed73 - <rustc_interface[2148282fb0834f58]::queries::Linker>::codegen_and_build_linker
  24:     0x74217a079b30 - rustc_interface[2148282fb0834f58]::passes::create_and_enter_global_ctxt::<core[436ac50667b45076]::option::Option<rustc_interface[2148282fb0834f58]::queries::Linker>, rustc_driver_impl[3a7877a37badcc56]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  25:     0x74217a0f19e0 - rustc_interface[2148282fb0834f58]::interface::run_compiler::<(), rustc_driver_impl[3a7877a37badcc56]::run_compiler::{closure#0}>::{closure#1}
  26:     0x742179f20608 - std[5b59e6f68f39e4a3]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[2148282fb0834f58]::util::run_in_thread_with_globals<rustc_interface[2148282fb0834f58]::util::run_in_thread_pool_with_globals<rustc_interface[2148282fb0834f58]::interface::run_compiler<(), rustc_driver_impl[3a7877a37badcc56]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  27:     0x742179f20ef4 - <<std[5b59e6f68f39e4a3]::thread::Builder>::spawn_unchecked_<rustc_interface[2148282fb0834f58]::util::run_in_thread_with_globals<rustc_interface[2148282fb0834f58]::util::run_in_thread_pool_with_globals<rustc_interface[2148282fb0834f58]::interface::run_compiler<(), rustc_driver_impl[3a7877a37badcc56]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[436ac50667b45076]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  28:     0x742179f222f7 - std::sys::pal::unix::thread::Thread::new::thread_start::hbb5e0f14d5ca8b98
  29:     0x7421740a370a - <unknown>
  30:     0x742174127aac - <unknown>
  31:                0x0 - <unknown>

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: please make sure that you have updated to the latest nightly

note: rustc 1.87.0-nightly (fd17deacc 2025-03-04) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z incremental-verify-ich=yes -C incremental=[REDACTED] -C debuginfo=2 -C link-dead-code=true -Z validate-mir

query stack during panic:
end of query stack
error: aborting due to 1 previous error; 1 warning emitted

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the reduced repr_simd example in the issue and inspect compiler/rustc_codegen_llvm/src/context.rs around handle_fn_abi_err and fn_abi_of_instance. Run the reported compiler command against the reduced program, then verify that this case no longer produces an internal compiler error.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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